(1) Field of the Invention
This invention relates to a novel single-ended screen-regulated cathode-follower output topology for implementing vacuum-tube audio power amplifiers to provide for the reproduction of high-fidelity music with minimal audible distortion.
The present invention is an improvement over the amplifiers disclosed in prior U.S. Pat. No. 5,859,565 entitled “CATHODE-FOLLOWER HIGH-FIDELITY POWER AMPLIFIER” issued Jan. 12, 1999, and prior U.S. Pat. No. 6,265,938 entitled “LINEAR HIGH-VOLTAGE DRIVE STAGE AND CATHODE-FOLLOWER HIGH-FIDELITY AMPLIFIER IMPLEMENTING SAME” issued Jul. 24, 2001. The present improvement resides in the novel combination of an output tube having its screen grid voltage regulated so as to maintain the plate-to-cathode current relatively immune to noise and distortion in the power supply, while providing all the advantages of the cathode-follower operation described in said patents and summarized herein below.
(2) Description of the Prior Art
In the past decade of the art of high-fidelity audio reproduction it has come to be recognized by many audiophiles and amplifier designers that vacuum-tube amplifiers can provide superior music reproduction as compared with transistor amplifiers. These tube amplifiers generally have output stage configurations which are either push-pull or single-ended. It is well-known that the single-ended topology has both advantages and disadvantages with respect to the push-pull topology. A primary object of the present invention is to provide a new single-ended topology which retains these advantages while obviating several major disadvantages.